1. Field of the Invention
The present invention relates to oil-filled protectors for use with electric motors and, more particularly, for use with electric submergible motors to be suspended within wellbores.
2. Description of Related Art
Electric submergible pumps are widely used throughout the world for recovering subterranean fluids to the earth's surface. For the long term successful operation of such submergible pumping systems, the electric motor must be supplied with uncontaminated cooling motor oil. This cooling oil is partially contained within one or more elastomeric bags within a motor protector.
Specifically, the elastomeric motor protector bags are generally cylindrical in shape and are sealed within an oil filled housing. The bags are filled with oil at the time of installation to an expanded state. With the rise of temperature caused by the immersion in the wellbore, as well as the thermal expansion caused by the operation of the electric motor, the bags tend to slightly expand even more. When the electric motor is turned off, the cooling oil cools and contracts. This contraction allows the motor protector bag to deflate. The repeated expanding and contraction of the elastomeric bag can cause splitting or cracks in the bag under certain conditions.
The cooling oil exits the bags for return to the electric motor through a series of openings or ports in a housing partially disposed within the bag. Under certain circumstances, the elastomeric bag can collapse when the cooling oil is exiting the bag, and contact and seal the ports. This blockage of the ports prevents the cooling oil from returning to the motor. Thus, the motor will operate at a higher than desired temperature, which can directly lead to shortened operational life, which in turn will cause the premature shutting-in of the well, and the costly removal and repair of the submergible pumping system.
There is a need for an improved elastomeric bag for use within an oil-filled electric motor protector that exhibits satisfactory elasticity, yet will not collapse against the oil return ports.